Biogenic VOC emissions under drought and temperature stress

As climate change brings warmer temperatures and reduced precipitation to forests globally, it is vital to understand how plants adapt to drought and temperature stress. Plant activity emits biogenic volatile organic compounds (BVOC), and stress-induced changes in BVOC concentrations have important implications on secondary VOC and aerosols formation due to atmospheric reactions with ozone and other oxidants. Measurements of BVOC emissions were made at the Biosphere 2 rainforest facility near Oracle, AZ, USA from September to December 2019. Time resolved BVOC vertical concentration gradients were measured continuously using  a proton transfer reaction time-of-flight mass spectrometer (PTR-QiToF-MS, Ionicon) sampling sequentially from five levels of a vertical tower positioned at 1 m, 3 m, 7 m, 14 m and 20 m above the forest floor. Emissions of a full range of primary BVOCs are estimated from concentrations and air exchange rates. The changes in ecosystem BVOC emission are evaluated under normal precipitation conditions, then throughout a controlled 2-month drought period, and finally through a re-wet period where rain was re-introduced to the rainforest. Analysis aims to show the vertical gradient of BVOC emissions from the forest plants, as well as how BVOC concentrations changed throughout the different stress periods. BVOCs that are important for plant physiology and atmospheric science, such as isoprene and higher terpenoids, as well as other compound classes such as volatile short chain and medium chain fatty acids, will be investigated in detail. These results will give insight into how plant emissions are affected under stress, either as protective mechanisms or due to desiccation-induced responses.